1. Field of the Invention
The present invention relates generally to advances in medical systems and procedures for prolonging and improving human life. More particularly, this invention relates to a method and apparatus for thermally treating the intervertebral disc to relieve pain associated with abnormalities of the disc due to pathology of the disc or interruption of the various neural processes in and around the disc.
2. Description of the Related Art
The use of radiofrequency electrodes for ablation of tissue in the body or for the treatment of pain is known. In a typical application, a radiofrequency probe or a resistive heating probe may be constructed in an elongated, cylindrical configuration and inserted into the body to a target tissue which is to be treated or ablated. In the case of a radiofrequency probe, there may be an exposed conductive tip portion and an insulated portion of the probe. When connected to an external source of radiofrequency power, heating of tissue occurs near the exposed conductive portion of the probe, whereby therapeutic changes in the target tissue near the conductive tip are created by the elevation of temperature of the tissue. Thermal probes can also be made by resistive heating of a portion of the probe so as to heat surrounding tissue by thermal conduction. By reference, the products of Radionics, Inc., located in Burlington, Mass., include commercially available radiofrequency generators and electrode systems of varied configurations. A paper by Cosman, et al, entitled xe2x80x9cTheoretical Aspects of Radiofrequency Lesions in the Dorsal Root Entry Zonexe2x80x9d, Neurosurgery, December 1984, Vol. 15, No. 6, pp. 945-950, describes aspects of tissue heating using radiofrequency electrodes and probes.
The use of thermal therapy in and around the spinal column is also known. Heating of an intervertebral disc to relieve pain is described in commonly assigned U.S. Pat. No. 5,433,739 entitled xe2x80x9cMethod and Apparatus for Heating an Intervertebral Disc for Relief of Back Painxe2x80x9d and in commonly assigned U.S. Pat. No. 5,571,147 entitled xe2x80x9cThermal Dennervation of an Intervertebral Disc for Relief of Back Painxe2x80x9d, the contents of each patent being incorporated herein by reference. In these patents, electrodes are described for either radiofrequency or resistive thermal heating of all or a portion of the intervertebral disc. Straight, curved, and flexible-tipped electrodes are described for this purpose.
U.S. Pat. No. 6,007,570 to Sharkey/Oratec Interventions discloses an intervertebral disc apparatus for treatment of the disc. The apparatus includes a catheter having a self-navigating intradiscal section in the form of a conventional helical coil. In use, the intradiscal section is advanced through the nucleus pulposus and is manipulated to navigate within the nucleus along the inner wall of the annulus fibrosis. An energy delivering member incorporated into the apparatus adjacent the intradiscal section supplies energy to treat the disc area.
The apparatus disclosed in Sharkey ""570 is subject to several disadvantages which detract from its usefulness in relieving pain associated with an intervertebral disc. For example, navigation of the helical coil of the catheter within the nucleus pulposus requires the support structure to wrap around in an approximately circular fashion from the anterior portion to the posterior portion of the intervertebral disc. This serpentinus path of the support structure is difficult for the surgeon to effectuate. Moreover, the configuration of the helical support structure increases the risk of probe kinking and is deficient in consistently facilitating the prescribed movement within the disc.
It is desirable to treat the posterior or posterior/lateral portion of the intervertebral disc for the indication of mechanical degeneration of the disc and discogenic back pain. Pain can be derived from degeneration or compression of the intervertebral disc in its posterior or posterior/lateral portions. There is some innervation of the intervertebral disc near the surface of the disc and also within its outer portion known as the annulus fibrosis. Mechanical damage such as fissures or cracks within the disc caused by age or mechanical trauma may result in disc innervation which is believed to be associated with painful symptoms.
Accordingly, the present invention is directed to a novel apparatus and method of use which provides for direct and confirmable placement of a thermal or electromagnetic field (EMF) treating element within the posterior/lateral and posterior portions of an intervertebral disc for thermal treatment. The apparatus includes a percutaneously introducable thermal application device having a novel configuration which provides excellent torque transmission and an increased flexure in a specific direction thereby facilitating the advancement of the thermal device within an intervertebral disc and preferably, for example, in the annulus fibrosus between layers of annular tissue.
The present invention is a novel and improved system and method for approaching the intervertebral disc through a percutaneous insertion from the back of a patient. In one embodiment, the surgical apparatus includes an elongated thermal or electromagnetic field creating probe member having a guidable region adjacent its distal end with an undulating groove defined in its outer surface. The undulating groove is dimensioned to facilitate bending of the guidable region in at least one radial direction preferably, opposed radial directions, of movement relative to a longitudinal axis of the thermal probe. Preferably, the guidable region includes a plurality of undulating grooves, whereby adjacent undulating grooves are longitudinally spaced with respect to each other. The undulating grooves each define a sinusoidal configuration which may be arranged about an undulating axis extending in oblique relation to the longitudinal axis. The guidable region includes a longitudinally extending backbone which facilitates the desired bending of the guidable region.
The apparatus may also include a cannula to facilitate introduction of the thermal probe into the intervertebral disc. The cannula defines a lumen to receive the thermal probe with the thermal probe being advanceable within the lumen. The cannula includes an arcuate end portion dimensioned to arrange the guidable region of the thermal probe at a desired orientation within the intervertebral disc at a target region, for example, within the annulus fibrosis. The cannula may define a penetrating distal end dimensioned to penetrate the intervertebral disc. Impedance measuring means are associated with the cannula to monitor the impedance of tissue adjacent a distal end of the cannula to provide an indication relating to tissue condition or type.
A preferred method for relieving pain associated with an intervertebral disc having a disc nucleus pulposus and an outer annulus fibrosis surrounding the nucleus pulposus is also disclosed. The method includes the steps of introducing a thermal or electromagnetic field (EMF) transmitting element of a probe into the annulus fibrosis of the intervertebral disc and supplying thermal or EMF energy from an appropriate source to the transmitting element to heat the annulus fibrosis adjacent the transmitting element sufficiently to relieve pain associated with the intervertebral disc.